Context

Recently we've hit quite a few times issues with unnoticed missing dependency flow or symbols publishing due to improperly configured default branch->channels association.

In such case the command succeeds with the message:

The build '{build.Id}' is already on these target channel(s):

This is missleading to untrained eye - especially in a long build output spew.

Instead we'd like to have an option to error out if the essociation is missing - and hence subsequently fail such build step.